Abstract: In multi-product pipelines, the pressure changes along the pipeline is mainly caused by the change of pipeline characteristic and products with different densities within the pipeline, the flow varies with time, which is decided by the pumping number, resistance and elevation. The variation of flow must generate with the movement of mixed contamination plug in the pipeline. In the paper calculation and analysis on the change law of frictional resistance along pipeline produced from different products with different densities for the pipeline have been made with hydraulic calculation equations combined with the case.